I. Field of the Present Invention
The present invention relates generally to fuel inducting systems for internal combustion engines operating in aircraft, and more particularly to such a system having a mechanical fuel induction apparatus as well as an electronic fuel injection means to form a back up in the event of an electrical failure.
II. Description of the Prior Art
There are many previously known fuel induction systems for internal combustion engines. However, the internal combustion engines used in aircraft primarily utilize a hydro-mechanical fuel injection system although some aircraft engines do use a carburetor for fuel induction. In a known manner, the carburetion system comprises throttle linkage which controls the amount of fuel delivered to a carburetor throttling passage to be used for ignition in the engine cylinders. The carburetor is coupled to a manifold which directs the fuel mixture to the cylinders. However, while such systems are generally capable of providing a sufficient amount of fuel to the cylinders for operation of the engines throughout a wide range of engine speeds, variation in the amount of fuel delivered to each cylinders, and variations in richness of the fuel mixture can waste fuel and cause inefficient operation of the engine.
In order to overcome the above mentioned problems, hydro-mechanical fuel injection systems have been devised so that a properly metered amount of fuel can be delivered to each cylinder as is necessary. In general, such systems include a plurality of injection nozzles corresponding in number to the number of cylinders in the engine, whereby fuel is injected directly into each cylinder by a nozzle. The operation of the injection system is manually controlled by hydro-mechanical apparatus which can be varied in response to changing engine operating conditions such as temperature and engine speed. Moreover, such systems can be especially advantageous for use in aircraft engines for the reason that adverse effects occur due to changes in ambient pressure such as altitude changes and gravitational effects during maneuvering, or due to changes in engine operating conditions. As a result, most aircraft engines of the internal combustion type utilize fuel injection systems as opposed to carburetion systems.
However, since the fuel injection systems are controlled by the pilot of aircraft, the pilot must continuously read guages and indicators pertaining to enging operating conditions and lean or enrich the fuel mixture according to set standards provided by the engine manufacturer after making such readings. Unfortunately, failure to make the adjustments recommended by the manufacturer can adversely affect efficient engine performance and substantially reduce engine life. In particular, leaning of the fuel mixture is desired for optimum operation at cruise power, but excessive leaning can cause excessively high cylinder temperature resulting in reduced engine life and possible destruction of the engine. Moreover, although electronic fuel injection systems have been used in land vehicles, they have not been considered well adapted for use in aircraft.
In view of the fact that electrical power is necessary to operate electronic ignition systems, it would heretofore have been necessary to provide such aircraft with a back-up electrical system to prevent engine failure in the event that the primary electrical system fails. Unfortunately, it is possible that conditions which cause failure of the primary electrical system can also cause failure of the secondary electrical system, thereby rendering the aircraft inoperable and thus putting the aircraft, its passengers and crew in great danger. Moreover, a back-up electrical system can be complex and expensive to install, especially when the system must operate more than fuel injection apparatus.